1. Field of the Invention
The invention relates to electronic device chip scale packages, and more particularly to isolation structures for CMOS image sensor chip scale packages (CIS-CSPs) and fabrication methods thereof.
2. Description of the Related Art
CMOS image sensor devices are used in a wide variety of applications, such as digital still cameras (DSC). These devices utilize an array of active pixels or image sensor cells, comprising photodiode elements, to receive electromagnetic radiation to convert images to streams of digital data.
Chip scale packages (CSPs) are designed for flip chip bonding to a supporting substrate, such as a package substrate, a module substrate or a printed circuit board (PCB). With flip chip bonding, bumps, pins or other terminal contacts on the package, are bonded to mating contacts on the supporting substrate. The bonded terminal contacts provide the physical and electrical connections between the package and the supporting substrate.
U.S. Pat. No. 6,917,090, the entirety of which is hereby incorporated by reference, discloses a chip scale image sensor semiconductor package, a method for fabricating the package, and systems incorporating the package. Forming bonded connections between the substrate bonding contact and the die bonding contacts by wire bonds or tape leads is however, tedious.
To solve the bonded connection problem, a shellcase semiconductor device chip scale package technique has been developed. U.S. Pub. No. 2001/0018236, the entirety of which is hereby incorporated by reference, discloses a semiconductor chip scale package technique. T-shaped connections between the substrate bonding contact and the die bonding contacts are provided. The T-shaped connections are protected by a passivation layer. After a wafer assembly is singulated by dicing it into a plurality of separate integrated circuit device packages, the T-shaped connection end, however, is exposed, resulting in weak spots vulnerable to corrosion and peeling. Thus, the integrated circuit device packages fail to pass reliability tests such as the high temperature/high humidity test.
FIGS. 1A-1B are cross sections illustrating conventional fabrication steps of dicing a chip scale package wafer assembly. Referring to FIG. 1A, a transparent substrate 10 configured as a support structure for a chip scale package comprises a CMOS image sensor die 20 with a die circuitry attached thereon. The CMOS image sensor die 20 comprises a sensor area with a micro-lens array 22 configured as an image plane. A passivation layer 24 is disposed on the micro-lens array 22. A spacer 15, defines cavity 18, between the substrate 10 and the CMOS image sensor die 20. An encapsulant 30 is formed on the substrate encapsulating the CMOS image sensor die 20. An optional structure 35, such as glass, is disposed on the encapsulant 30 to strengthen the package. A T-shaped connection 40 extending from the die circuitry to a plurality of terminal contacts 70 for the package. The T-shaped connection 140 connects the substrate bonding contact (not shown) to the die bonding contacts 25. A buffer layer 50 is disposed on the T-shaped connection 40. The T-shaped connection 40 is protected by a passivation layer 60.
Referring to FIG. 1B, the resulting wafer scale assembly 1 is diced to yield a plurality of packaged integrated circuit devices 1A and 1B. One end of T-shaped connection is exposed resulting in weak spots vulnerable to corrosion and peeling. The exposed T-shaped connections encounter problems of corrosion and peeling due to moisture penetration. Thus, the integrated circuit device packages fail to pass reliability tests such as the high temperature/high humidity test.
An isolation capable of preventing exposed connections from moisture penetration damage, has long been sought.